Centralized traffic controlling system for railroads



T. J.- JUDGE June 28, 1938.

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Feb. 26, 1934 3 Sheets-Sheet 1 INVENTOR 5 55m 1 22L nil.- :11. i I. M .56 u 3.5.20.

llllllzlL T. J. JUDGE June 28,1938,

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS s sheets-sheet 2 Filed Feb. 26, 1934 Y hm R E m MW T n m m m v Q L u i n w m hm u v aim 3 u mm n wm l v um E. m m E r f 3 6 FIG. 2..

June 28, 1938. I J JUDGE 1 2,121,801

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Feb. 26,1934 s Sheets-Sheet 5 i I 11o-fl 127 mus #128 INVENTOR -BY I Patented June 28,1938

, UNITED STATES TRALIZED TRAFFIC CONTROLLING C'EN SYSTEM FOR RAILROADS Thomas J. Judge, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

I N. Y. Application February 26,

34; Claims.

This invention relates to centralized trafiic, controlling systems forrailroads and it more particularly pertains to the cooperation of the communication part of such a system with the trafiic 5 controlling devices at field stations.

In a centralized trafiic controlling system of the type contemplated by the present invention communication is established between a central control oflice' and a number'of field stations by means of a selective coded type communication system. In such a system aplurality of series of coded impulses are transmitted over the line circuit which connects the control office with the field stations. The first or earlier part of each series of code combinations is employed for the selection of the station, while the last or later part of each different series of code combinations is employed to govern the traffic controlling devices at the selected station. Y

The present invention is directed'more particularly to the manner in which the later part of each different series of coded impulses or combinations is arranged to select. and control the required route for governing ,trafiic over such route. I More specifically a track switch is governed in accordance with the conditions of switch control relays which are positioned in accordance-with the reception of coded impu1ses. Similarly the signals are governed by signal control relays which establish the direction for the traffic to proceed over the particular route as determined by the position of the track switch. These signal control relays are likewise positioned in accordance with the reception of coded impulses. 'The particular route over the track switch for such direction is, dependent upon a selection which requires correspondence between the control relays and the track switch as repeated by the switch repeating relay. I

The control-relays are selectively energized in accordance with the code combinations received I ,fromthe control office, such combinations being repeated by the position assumed by the station line relay at the selected station during. the later part, of each different series of code combinations. 1 Upon reception ofa series of code impulses one control relay or the other will be selected uponeach step of the step-by-step selecting system in accordance with the character lpolarity) of the impulse for that step. Proper stick circuits are provided for these control relays and the selecting circuits are so arranged that only one of the relays selectable at each step may be energized at any one time. Inthe event of trouble 55: conditions on the'circuits causing more than one practice.

1934, Serial No. 712,920

relay per step to be picked up or in the e'vent'that neither relay is picked up, the switch is not opercontrolled, so that the route clearing circuits are checked with a minimum amount of control equipment such as relays and the like and in which provisions are made to obtain the maximum safetyrequiredin the operation of railroad traific controlling systems without undue circuit com,

plications. I

Other features of the present invention reside in the various detailed circuit arrangements particularly adaptable for systems of this'type.

These characteristic features thus briefly stated will be explained more in detail in the following description of one embodiment of the invention while various other characteristic features, functions and advantages of a system embodying the present invention will be in part pointed out and in part apparent as the description progresses. g

In describing the invention in detail reference will "be made to the accompanyingdrawings in which the various parts are designated by suitable reference characters and in which:-

Figs. 1, 1A, and 2 diagrammatically show the apparatus and circuits provided at a typical field station for the control of a single track switch and the signals for governing traffic thereover.

Fig. 2 is partly a duplicate of Fig. 1 and is for the purpose. of showing how the SO relay and the stepping relays of Fig. 1 are controlled. The relays of Fig. 2 are given the same letter reference characters as corresponding relays; of Fig. 1, but with the exponent 2 added. Similarly, the same reference numbers have been applied to the con- 'tacts of Fig. 2 as used for corresponding contacts of Fig. 1 but with the preceding numeral 2 added.

For the purpose of simplifying the illustration and facilitating in the description the various parts and circuits have been shown diagrammatically with certain conventional illustrations employed. The drawings have been made more with the purpose of setting forth an easy and clear. understanding of the principles and mode of a operation of the invention rather than attempting to illustrate the specific construction and ar rangement of parts that would be employed in Therefore the variousrelays and their contacts are illustrated in a conventional manner, symbols being used to indicate connections to the sources of current, with the complete wiring connections to these terminals omitted.

The symbols and are employed to indicate the positive and negative terminals, respectively, of suitable batteries or other sources of direct current and the circuits with which these symbols are used always have current flowing in the same direction.

Communication system in generaZ.A centralized traffic controlling system in which the present invention is particularly useful consists of a control ofiice and a number of field stations. Communication is established between the control ofiice and the field stations for the transmission of controls for governing the traflic controlling devices at these stations. Likewise communication is established between the stations and the control office for the transmission of indications from one station at a time, to give the operator in the control ofiice information respecting the location of trains and the response of the various traffic controlling devices. This communication is established over a station selective coded type system in which a small number of line wires is employed and in which the selective communication between the office and any particular station for the transmission of outbound controls or the transmission of inbound indications is accomplished by the transmission of suitable codes. V

For the purpose of illustrating the present invention it is not believed necessary to show the apparatus in the controlofiice which functions to impress aplurality of series of different code combinations onthe line circuit in accordance with the positions of code jumpers and control levers. Neither is it believed necessary to illustrate the reception at the control ofiice of code combinations of impulses controlled from the field stations, it being assumed that a system for accomplishing these purposes may be of any suitable type such, for example, as that shown in the prior application of T. J. Judge, Ser. No. 613,353, filed May 25, 1932.

With reference to Fig. l, a control office has been indicated by a dotted rectangle in the upper left hand portion of the drawing. Three line wires, including control line H], indication line l2 and common return line l4, connect the control ofiice with the field station. It will be understood that these three line wires extend to each of the outlying field stations of the system in series. The field station illustrated in Fig. 1 includes additional equipment required to effect the step-by-step operation of the system and the selection of the station, such additional equipment being more fully illustrated in Fig. 2.

The control wires and the common return wire are so organized that they provide two line circuits, namely, a control line circuit and an indication line circuit. The control line circuit is the circuit over which the transmission of impulses from the control office is accomplished. These impulses are of selected polarity for positioning a three position, polarized, biased-toneutral line relay F, one of these line relays being located at each field station. It will be assumed that a impulse applied to line in positions relay F to the right, a impulse applied to line it positions relay F to the left and the deenergization of line l positions relay F to its neutral position, as indicated in Fig. 1.

The transmission of a series of distinctive impulses over the control line circuit results in the step-by-step operation of a stepping relay bank at each field station irrespective of the polarity of the impulses, while the polarity of the impulses determines the particular field station to be selected. A station selecting relay S0 at each field station is energized at the beginning of each cycle of operations and remains energized during the first or station selection part of the cycle only so long as the code combination of impulses applied to the control line circuit corresponds with the code combination assigned to the corresponding field station, as determined by the selective. connection of the jumpers at the field station. When the polarity of an impulse received at a station'does not correspond with the code combination at this station as determined by the jumper connection, relay S0 at that station is deenergized, thereby rendering in- I effective the succeeding impulses of a particular cycle. At the particular station where the SO relay remains energized at the end of the station selecting portion of the cycle the remaining impulses of that cycle are effective to select and establish proper control conditions, because the SO relay then remains energized during the remaining portion of the cycle.

Similarly, for the transmission of indications to the control office only one station can transmit over the indication line circuit during an operating cycle. The station which is permitted to transmit is selectively connected to the communication system throughout a cycle of operations by means of some lock-out arrangement or superiority of code plan. In any event the selection of afieldstation for transmitting in-bound indications is made effective in such field station by the continued energization of its selecting or lock-out relay throughout the cycle of operations. Since the present invention is not concerned with the transmission of in-bound indications the detailed circuit arrangements and method of operation for this portion of the system is omitted, it being considered immaterial for an understanding of the present embodiment.

Field station apparatus.-The field station includes, besides the above mentioned line relay F, a. neutral line repeating relay FP of the quick acting type which repeats the energizationsof line relay F irrespective of the polarity of the impulses which energize the line relay.

A- slow acting neutral relay SA defines the bounds of the operating cycle of the system, since it is picked up at the start of each cycle and dropped at the end of each cycle. During the impulses of the line circuit as repeated by the comparatively rapid operations of relay FP, relay ,SA is maintained in its picked up position due to its slow acting characteristics.

As above mentioned relay S0 is in its picked up position during the transmission of controls in the later portion of the cycle only at the selected station. The field station has a bank of stepping relays which mark off the individual steps of the operating cycle. -These relays indicated 3V, 4V and 5V, have their control circuits omitted from Fig. 1 for the sake of simplicity and likewise stepping relays IV and 2V have been omitted from 1 since it is assumed that station selection is eifected during the first two steps of the cycle. The detailed operation of the SO and stepping relays will be explained in connection with Fig. 2.

The field station includes two neutral switch control relays WN and WR. Relay WN controls the operation of the switch machine to its normal position and relay WR controls the operation of the switch machine to its reverse position.

switch. I The switch machine SM is controlled by relays WN and WR subject to suitable approach locking means, one type of which is indicatedby approach locking relay AL shown in dotted lines. Such approach locking may be provided with time release and an approach locking repeating relay, for example, as shown in the prior application of N. D. Preston, Ser. No. 573,079, filed November 5, 1931.

The track switch TS has the usual closed circuit detector track section, with track relay T and track rep-eater relay TP normally energizedv to repeat the unoccupied condition of the associated track section. When the associated track section is occupied these two relays are dropped in sequence, with the response of relay TP being slightly delayed after it is deenergized'bec'ause of its slow acting characteristics.

tion. Correspondence'relay WNCR repeats the condition that the track switch is in correspondence with the switch control relay WN. Correspondence relay WRCR. repeats the condition that-the track switch is incorrespondence with the switch control relay WR.

Suitable signals IA, IB, 2A and 2B are provided for governing traffic over the track switch in accordance with the usual practices. These signals are normally at stop" since the corresponding signal controlling relays IAG, IBG, ZAG and 2BG are normally deenergized. When a signal control relay is energized the corresponding signal is transferred from astop to a clear indication. Such signal control is governed by traflic conditions in accordance with suitable approach look ing as is the practice in such systems.

' Lock'relay L performs the function of providing locking between switches and signals. but preventing the operation of a switch when for any reason it is improper for that switch to be oper- 1 ated. Relay, L likewise governs the operation of the signal control relays in such a way that a signal cannot be cleared until theswitch is locked againstoperation. Cooperating with the signal control relays are right and left auxiliary relays RM and LM. Either one of these relays in its deenergized position locks the switch control circuits by dropping relay L. Their control is such that when a signal control relay which controls signals to .the right is picked up relay RM is dropped and when a left signalcontrol relay is picked up relay LM is dropped.

Stop relay S is provided for controlling relays LD and RD so that upon the reception of the proper code, relay S is picked up to drop whichever direction relay is stuck up so that both direction relays will be deenergized for putting all signals to stop. Although the field station is illustrated asincluding only'a single track switch TS it is to be understood that any number of track switches may be similarly controlled. Track switch:TS is operated'from one extreme locked position to the otherby'a'suitable switch machine SM which may be of any desired type known in the art.

Various other'apparatus and devices for the field station includes bus wires, circuit connections, over load protection, terminal blocks and such other equipment as may be necessary in actual practice, all of which has been omitted from the present drawings in order that the disclosure maybe as simple as possible.

It is believed that further characteristic functions and features of the present invention will be best understood by further description being given from the standpoint of typical operations.

Operation For the transmission of controls a plurality of distinctive code combinations are applied to the control line circuit'in the control office, each code combination comprising a plurality of distinctive impulses. In the present disclosure these impulses are distinctive byreason of their polarity.

. In the description and code table'which follows,

the circuits selected by relays 3V, 4V and 5V, are chosen on thethird, fourth and'fifth steps respectively, since'these three stepping relays are operated on the next three steps after station selection in the typicalsystem assumed for purposes of this description. The first portion of each difiierent series of cod combinations comprises What may be termed a station code'call for the selection of aparticular station, while the later portion of each different series forms control codes transmitted to the selected station. Thus the control codes for the several stations differ only with respect totheir. different functions at these stations and they are selectively associated with the particular station. desired by reason of the preceding station selecting code call.

' With the possibility of there being either a positive ora negative impulse for each step the number of code combinations equals two raised to the CPI power of the number of steps. Each one of these Table of control codes Code used Third Fourth I step Not used.

Not used. {Switch normal.

Signals left.

Switch reverse.

Signals left. {Switch normal.

Signals right.

{Switch reverse. 7 Signals right. r {Switch normal. v v r S1gnals stop.. 8 j {Switch reverse.

""7 Y S1gnals stop.

The code combination received at the station on the third step is effective to control the direce tion control relay LD and the code combination received on the fourth step iseflective to control direction relay RD. In other words, the reception of a combination on the third step picks up relay LD and this relay sticks upuntil the track is occupied or until a stopcode is received.- 'Thereception ofa impulse on the fourth step picks up relay RD and it also sticks up until the track is occupied or until a stop code is received. The reception of a impulse on the third step is not effective unless relay LD is picked up and the reception of a impulse onthe fourth step is not effective unless relay RD is picked up. From this it will be observed that a stop code consists of on the third and and fourth steps.

The code combination received on the fifth step is effective to control the switch machine control relays WR and WN. A impulse on the fifth step picks up relay WN and a impulse on the fifth step picks uprelay WR in a, manner which will be described in detail later.

More specifically there is a group of control levers in the control ofiice for each station. The positioning of these levers for a particular station followed by the actuation of suitable means to initiate the system causes the transmission of a series of impulses comprising the code call for that station, followed by the control code combination for selecting the route at that station. Assuming one three position signal lever and one two position switch machine lever associated with a particular station it will be obvious that there are six combinations of these two levers requiring the transmission of six code combinations to the station. This leaves two code combinations of the eight which may be used for other purposes or which may be used in duplicate, as indicated by code numbers 3 and 4 in the code table accomplishing the same results as code numbers 1 and 2.

It is assumed that the codes are transmitted when the control levels are in proper positions to effect the desired'control conditions at the field station as assigned to each code combination in the above table. For example, if the switch lever is normal and the signal lever is in an east clearing position the fifth code is transmitted consisting of to position the track switch TS in its normal position and to clear east bound signal IA. Other codes and the results accomplished by their transmission will be obvious from the above code table.

Station selection and step-by-step operation.- At the beginning of a cycle of operations relay FP (see Fig. 2) is energized by polar contact 2 of relay F in either a right or a left hand dotted position, depending upon whether the line is energized with a or a impulse respectively. The closure of front contact 2I3 of relay FP energizes relay 8A which picks up after a short time and remains picked up throughout the cycle and until the control line has been deenergized for a predetermined period of time at the end of the cycle.

It will be assumed that the control ofi'lce selects the station illustrated in the present drawings by applying a conditioning impulse to the line for picking up the SO relays, followed by a code combination of and impulses on the first and second steps respectively for maintaining relay SO (S of Fig. 1) picked up throughout the cycle. The conditioning impulse closes a circuit for picking up relay SO which extends from back contact I09 of relay 8A front contact I08 of relay FP contact 2H of relay F in its right hand dotted position, back contacts H8, H9, 230, I01 and I06 of the stepping relay bank and lower winding of relay S0 to During the next time space period following the conditioning-impulse and also during all other time space periods between impulses,

relay S0 is stuck up over a circuit extending from front contact I09 of relay SA front contact 2 I6 of relay S0 make-before-break contact 2II of relay F in its neutral position, front contact I04 and upper winding of relay S0 to Since it is assumed that the station illustrated in. Fig. 2 is selected during the first two steps of the stepping relay bank, relay SO will remain energized during the impulse periods of the first two steps and when. relay 3V is picked up during the time space which succeeds the second impulse, a stick circuit is closed for maintaining relay SO stuck up throughout the remainder of the cycle which extends from front contact I03 of relay 3V front contact I04 and upper winding of relay S0 to Since the station code call for selecting the station of Fig. 2 is code jumpers IIO, III, H2 and H3 will be in the positions illustrated.

In response to the first time space following the conditioning impulse a circuit is closed for picking up relay IV which extends from front contact 2I5 of relay SA back contact II5 of relay FP front contact II6 of relay S0 back contact II! of relay VP back contacts H8 and MS of relays 4V and 2V respectively and winding of relay IV to Relay IV closes a stick circuit for itself extending from front contact 2 l5 of relay 5A front contact I I4 and windingof relay IV to which stick circuit is maintained throughout the cycle of operations. It will be obvious that similar stick circuits are completed for the other stepping relays of the bank at similar front contacts, therefore the stick circuits of these other relays will not be pointed out in detail.

During the first impulse period following the picking up of relay IV the selecting circuit for relay S0 is energized for maintaining relay SO picked up, which circuit extends from front contact I29 of relay SA front contact 2I'6 of relay S0 contact 2H of relay F in its right hand dotted position, back contacts 2I8, 2I9, 230 and I01, front contact I06 of relay- IV code jumper III and lower winding of relay S0 to It will be obvious that, at those stations with their code jumpers corresponding to jumper III in the alternate or open position, the SO relays will be dropped out at the first step. It will also be obvious that, in the event of a impulse received on the first step, the circuit through contact 2I'I in its left hand dotted position will be incomplete at open jumper II 3, so that relay SO would be dropped out at this step.

On the second step of the cycle the impulse is eifective to maintain relay SO energized over a similar circuit to that previously pointed out, except in this case it extends through contact 2I'I of relay F in its left hand dotted position, front contact I20 of relay 2V and code jumper II2. From the above explanation it will be obvious-how relay SO (S0 of Fig. l) is picked up and maintained in its picked up position throughout a complete cycle of operations when the code combination received over the line circuit corresponds to the code combination of the illustrated station.

The first impulse following the time space which picked up relay IV is effective to pick up relay VP over a circuit extending from front contact II5 of relay SA front contact I2! of relay FP back contacts I22, I23, I24, I25, front contact I26 and. winding of relay VP to Relay V1 closes a first stick circuit for itself for the purpose of maintaining this relay energized during the next tirnes pace period,

which circuit extends from front contact H5 of relay SA front contact I26 of relay VP and over the remainder of the previouslydescribed circuit to the winding of relay VP The next time space is effective to pick up re- .lay 2V over a circuit extendingffrom front contact 2I5 of relay 5A back contact II5 of relay FP front contact II6 of relay S0 front contact III of relay VP back'contact I2I of relay 5V back contact I28 of relay 3V front contact I29 of relay IV and winding of relay 2V to During this time space period relay-V1 is stuck up over its secondstick circuit which-extends from. front contact H5 of .frelay' 8A back contact I:2I of relay FP front .contact I30 and winding of relay VP? to j .During the following impulse per'iod relay VP isde-energized because its'first described stick circuit is open at back" contact I25 of relay 2V and its seconddescribedstick circuit is open at I back contact I2I of relay FP The next succeeding time space is 'eiiective to pick up -relay 3V over an obvious'circuitwhichincludes the previously described pick-up circuit for relay IV but in this instance it extends through front contact -I-I9 of relay 2V It is believed that-the above explanationof the VP relay operation, together with the operations of the firstthree s'tepping'relays is suflicientto tion of the stepping relay bankillustrated in Fig. 2. It will be observed'that, at the nonselected stations (S0v relays down) steppingis discontinued'because"of op'en'front contacts similar to contact II6.' It will also be observed that the energizedsteppin-g relays will be de-energ'ized at the end of the cyclewh'en relay SA drops and opens its front contacts I I5 and 2I5. Relay SO will be de-energized; when relay 3V drops and opens its front contact I03.

Reception of control 'codes'r- -Assuming that the stepping relays are 'suitably picked up during the :deenergizedperiods following each 'jimpuls'e then. vthe polarity of" the next impulse. is effective to condition the control relays fo-rythat "step. For example, if the third impulse of aicontrolcode is relay LD will be energized and if the fourth impulse'of a control code is relay RD will be energized.

Referring to Fig. l, the energizing circuit for relayLD extends from front contact I6 of relay SO, contact I! of relay F in its right hand dotted position, back contacts I8 andQIS of relays 5V and 4V respectively, front contact 36.

' of. relay 3V, back contact 3| of relay RD and back contact I8 of relay 5V, front contact I9. of relay 4V, back contact 29 of relay LD, and. upper winding of relay RD to closes astick circuit for that particular relay T he picking up of either relay LD .or, RD

extending from (+),,ifront contact 89 of relay TB, conductor 90, back contact 3'I.of relays,

vand either front contact 38 or front contact 39 ofv relayLD or relay RD, through the lower wind -ing of the. associated. relay to This stick circuit is effective to maintain the 'direction're layenergized until a stop code is received which {picks' up relay S or untilthe track section is oc cupied; which drops rrel'ay' TP. Relay T1? is dropped by the opening of frontcontact 88 of relayT. Upon the reception'of a third impulse of character, with relay LD picked up, the stop relay is picked up over acircuit extending from front contact I6 of relay SO, contact H of relay F in its left hand dotted position, back contacts 32 and 33 of relays 5V and 4V respectively, front contact 34 of relay 3V, front contact 35 of relay LD and winding of relay S to Or'if relay RD is in its energized position from the previous cycle, then the reception of a relay S over the first portion of the above described circuit which'is now completed through front contact 33. of relay 4V and frontcontact 36 of relay RD to the winding of relay S.

The picking up of relay S opens the stick cir- 'cuit of both direction relays at its back contact 37 so that the particular one of these relays which is energized will be dropped, which results If the control code received on the fifth step i relay WN is picked up over a circuit which extends from (+),-front contact I6 ofrelay SO, contact'I'I of relay F in its right hand dotted; po-

sition, front contact I8 of relay 5V, lower windfourth impulse of character picks up stop 7 ing of relay WN, conductor 9| and front contact 56 of relay L to If the control code received on-the fifth step is I I relay WR is picked up over a circuitextending from ,front contact 16 of relay SO, contact I! of relay F in its lefthand 'dotted position, front contact 32 of relay 5V, lower. winding of relay WR, conductor! and front contact 56 ofrelayLto The picking up of relay'WR closes a-stick cir-. .cuit for itself through its lower winding extending from front contact. 40 of relay WR, back contact 4| of relay WN, lower winding of relay WR, conductor9l and front contact56 closes a stickcircuit' for itself through its lower .winding, extending from. frontcontact 42 of relay WN, back contact 43 of relay WR, lower winding of relay WN, conductor 9| and front contact 56 of relayL to The picking up of relay WN connects battery B through frontcontacts58 and 59 of lock reof relay L to The picking up of relay WN lay Lto the switch machinein such a direction that it will be actuated to its normal, locked position. The picking up of relay WR connects --battery B in areverse direction through front contacts 58 and'59 of relay Lto-the switch machine for actuating this machine to its reverse,

locked position. This positioning of the switchv machine is of course, subject to suitable approach and'detector locking in accordance with usual practices for preventing the operation of fa tra'ck switch to a new position underiunsafe conditions.

From the above description it will'be noted that the particular switch' control relay which circuit forrelay L extends through' front con tacts 16 and '82 of relayscLMand RM" respecsition. as long as relay L;is deenergized. The a tively, back contacts Stand 65 of relays WRCR and WNCR respectively, front contact 61 of relay TP and front contact 68 ofrelay AL.

Thisseries circuit for relay 3L provides a lock against switch machine operation by preventing a change in the switch machine control relays as long as the approach locking circuit (represented by contact 68) is interrupted, as long as the track is occupied (contact 61 of relay TP open), as long as the switch machine and its control relays are in correspondence (contacts 65 and 83 of the correspondence relays being picked up) and as long as any signal indicates clear (contact 16 or 82 being open). The switch machine is further checked against operation when the lock relay L is deenergized by contacts 58 and 59 of this relay opening the circuit leading to battery B and placing a short circuit across the switch machine operating wires.

Either switch control relayWN or relay WR is stuck up while a signal iscleared by means of stick circuits through the upper windings of these switch control relays and their front contacts 54 and 55 to at either front contact 52 of relay LD or front contact 53 of relay PD. The switch control relays have additional stick circuits controlled by switch repeating relay WP as will now be described.

When a train is engaged in switching operations ov-er track switch TS itAs advisable that the switch machine be controlled by hand. In

this event the trainman operates the selector lever and the hand throw lever of the switch machine for operating the track switch to the desired position. The operation of the selector lever of the switch machine unit functions to open the controlling circuits of the switch machine and the switch machine repeating relay by opening contacts 46 and 41. The opening of contact 4'! drops the neutral contact of relay WP'which closes a circuit for picking 'up the control relay as determined by the position of the track switch when the hand operation takes place.

Assuming that the track switch is in its normal locked position when this operation is 'effected, the dropping of relay WP closes a circuit for picking up relay WN which extends from back contact M of relay WP; contact 45 of relay WP in its left hand position, conductor 95, back contact 43 of relay WR, lower winding of relay WN, conductor 9| and front contact 56 of relay L to Relay WN sticks up by means of its front contact 92 as previously described. The construction of the switch machine is such that energy must be applied to its operating circuit conductors H and F8 in order to lock the machine. After; the above mentioned switching operations are complete the trainman restores the selector lever to normal which closes contacts 46 and 41 but since the switch machine is not locked by this operation contact 44 of relay WP does not pick up.

The occupancy of the track section by the train in question of course drops relays T and TP which drops relay WN, because relay L opens its front contact 56 when relay TP opens its. front contact 61. When the track section becomes unoccupied (irrespective of the position in which the switch machine was left) relays TP and L arep-icked up and is applied through front contact 56 of relay L to the lower windings of relays WN and WR. Since relay -WP is deenergiz ed and its contact 55 is still in its left hand position the above described circuit .is effective to pick up and stick relay WN. Current is then applied to the switch machine through front contacts 20 and 2! of relay WN, back contacts 49 and 51 of relay WR and front contacts 58 and 59 of relay L to the switch machine operating conductors Tl and 18 for operating the switch machine to its normal locked position. Relay WP now picks up its contacts 44 and 64.

Relay WNCR is now picked up over a circuit extending from contact 63 of relay WP in its left hand position, front contact 64 of relay WP, conductor 96, back contact 56 of relay WR, front contact 5| of relay WN, conductor 98 and winding of relay WNCR to The opening of back contact 65 of relay WNCR drops relayL which opens front contact 56 for dropping relay WN. The dropping of relay WN then drops relay WNCR. so that the circuits are in the same condition as when the switching operations above mentioned were started.

In the event that the track switch is in its reverse locked position when local switching operations are initiated then the dropping of contact 44 of relay WP picks up relay WR over a circuit extending through contact 45 of relay WP in its right hand dotted position. Relay WR will stick up until the switch machine is placed in its reverse locked position and repeated by the picking up of relay WRCR over the circuit which has been previously described. The opening of back contact 83 of relay WRCR drops relay L which opens contact 56 to drop relay WR which in turn drops relay WRCR to restore the circuits to the condition they were in when these local switching operations were initiated.

It is obvious that the switch machine will be returned to the position from which it was operated, whether this position was normal locked or reverse locked, because the control relay WN or the control relay WR will be picked up and stuck up until the switch reaches the corresponding position.

It will be observed that the third and fourth steps of the control code selects the signal control relay, the third and fourth steps of the control code selects the stop relay and the fifth step of the control code selects the switch control relay. From the above explanation. it is obvious that a switch can be operated to either position without clearing a signal by the transmission of the. proper stop code.

The various routes set up and the operations which result from the reception of each code (except the first two which are not used) may be best understood by considering each code combination individually. The circuits for picking up and sticking the control relays and for operating the switch machine have already been described so that this portion of each code combination will not be explained in detail.

Consideration of code number 3. on the third step picks up relay LD and it sticks up. on the fourth step is inefiective since front contact 36 of RD is now open. on the fifth step picks up relay WN and it sticks up. With relay WN up and relay WR down the switch machine is operated to its normal locked position. Relay WNCR is picked up over a circuit extending from contact 63.of relay WP'in its left hand position, front contact 64 of relay WP,'conductor 96, back contact 50 of relay WR, front contact 5| of relayWN, conductor 98, and winding of relay WNCR to The opening of back contact 65 of relay WNCRZ drops lock relay relay L, conductor 99, back contact 60 ofrelay verse locked position.

"as long as signal IA is clear.

LQReIay'ZAG' is picked uptofclear signal 2A over a circuit extending from front contact 69 of relay-TP, back; contact 66 of relay L,

conductor '99, back contact 60 of relay RD, front contact 6! of relay LD, conductor 91, back contact 84 of relay WRCR, front contact 85 of relay WNCR, and-winding of relay ZAG to The opening of back contact 14 of relay 2AG drops relay LM which maintains the circuit of lock relay L open as long as signal 2A is clear.

Consideration of code number 4. on the third step and onthe' fourth step are effective as in code number 3, for picking up and sticking relay LD. on the fifth step picks up relay WR and it sticks up; With relay WR up and relay WN down the switch machine is operated to its reverse locked position. Relay WRCR is now picked up over a circuit extending from front contact 50 of relay WR, conductor 96, front contact 64 of relay WP, contact 63 of relay WP in its right hand dotted position and winding of relay WRCR to The opening of back contact 83 of relay WRCR'drops lock relay L. Relay 2BG is picked up to clear signal 213 over a circuit extending from front contact 69 of relay 'IP, back contact 66 of RD, front contact 6| of relay LD, conductor 91, back contact 85 of relay WNCR, front contact 84 of relay WRCR and winding of relay 213G to- The opening of back contact 15 of relay 2BGdrops relay LM which maintains the circuit -of lock relay L open as long as signalZB- is clear.

Consideration of code number 5. on the third step is inefiective because front contact 35 of relay LD is open. on .the fourth step picks up relay RD and this relay sticks up.

on the fifth step picks up and sticks relay WN as in code number 3. With relay WN up and relay WR down the switch machine is operated to its-normal locked position.v Relay WNCR is picked up 'over the circuit described, in connection with code number 3 and relay L is dropped in the previously described manner.

Relay IAG is picked up to clear signal IA over a circuit extending from front. contact 69 of relay TP, back contact66 of relay L, conductor 99, back contact 6! of relay 1D, front contact 60 of relay RD,'conductor llll'l, back contact 62 of relay WRCR, front contact 12 of relay-WNCR and winding of relay lAGto The opening of back contact 8| of relay IAG drops relay RM which maintains the circuit of lock relayL open Consideration of code number 6. on the third step is ineffectiveas in code number 5. on the; fourth step picks up and sticks 'reon the fifth number 4. Withrelay WR up and relay WN down the switch machine is operated to its re- Relay WRCR is picked up over the previously described circuit andlock relay L is dropped as previously explained. Relay IBG is picked up to clear signal [3 over a circuit extending from front contact 69 of relay TP, back contact 66' of relay L, conductor 99,

back contact 6| of relay LD, front contact 60 of relay RD, conductor lllil. back contact 12 of relay WNCR, front contact 62 of relay WRCR and winding of relay IBG to- The opening of back contact 81 of relay lBG 'drops relay RM which maintains the circuit of lock relay L open as long as signal IB' is clear.

- Consideration of code number-7. -Sincethisis 'one that is energized will be dropped.

the direction relays LD or RD is picked up, so that the on either the third'step or the fourth step is effective to pick up relay S. The

opening of back contact 31 of relay S opens the stickxcircuit of both direction relays so that the on the fifth step picks up relay WN and it sticks as in other similar codes and the switch machine is operatedto its normal locked position as previously described. Since neither direc-v tion relay is picked up none of the signal relays can be operated at this time.

Consideration of code number 8. The code on the third and fourth steps is effective as in code number '7 while the on the fifth step is effective to pick up and stick relay WR, so

that the switch machine is operated to its reverse locked position all of which hasbeen previously explained.

When the train passes on to the illustrated track section relays T and TP drop in sequence.

cation part of the system has not been considered but'only the complete control operation has been outlined. After the last step hasbeen taken the control line circuit is deenergized in the control office for a prolonged period of time so that relay SA at each field station returns to a deenergized position because of open front contact 2l3 (see Fig. 2).

The dropping of relay S A causes the stepping relays and relay S0 to be deenergized because of open front contacts 2I5, H5 and I09. The

particular direction control relay L1) or RD that ispicked up is maintained energized until the track circuit becomes occupied or until a stop code' is received. The particular switch control relay WR or WN that is picked up is maintained energized until both direction control relays are I in their normal positions and also until lock relay L is dropped to lock the switch machine against further operation. The actuated correspondence relaYWNCR or WRCR is maintained energized until relay WP indicates that the switch machine is unlocked by droppingits front contact 64 or until relay WP indicates that the switch machine is out of correspondence with an actuated switch control relay, all of which will be obvious from a consideration of the operating circuits of these various relays as previously pointed out.

Having thus described a centralized traffic controlling system as one specific embodiment of the present invention it is desired to 'be understood that this form is selected to facilitate in the disclosurefof the invention rather than to limit the number of forms which it may assume and it is to be further understood that various modifications, adaptions and alterations may beapplied to the specific form herein-shown to meet the requirements of practice without in any manner departing from the spirit or scope of the invention except as limited by the appended claims.

What I-claim is: l 1. In'combi'nation, a line circuit having a plurality 'of--'c'ode "combinations applied thereto, a

machine for controlling said track switch, a plurality of signals for directing traflic over said track switch, a plurality of switch control relays for controlling said switch and a plurality of signal control relays for controlling said signals, means responsive to a first code combination for selectively actuating one of said switch control relays, means for restoring the actuated switch control relay to normal after said switch machine attains a position corresponding to said first code combination, means responsive to a second code combination for selectively actuating one of said signal control relays, means for restoring the actuated signal control relay to normal after its response to said second code combination only in response to the occupancy of said track section, and means for restoring the actuated switch control relay to normal only after the actuated signal control relay is restored to normal.

2. In combination, a line circuit having a plurality of codes applied thereto, a track switch, a signal for clearing trafiic over said track switch, a switch control relay actuated by one of said codes for governing said track switch, a signal control relay actuated by another of said codes for energizing said signal, acorrespondence relay energized only if there is correspondence between said track switch and said switch control relay, and means responsive to the energization of said correspondence relay for releasing said actuated switch control relay unless said signal control relay is then energized.

3. In combination, a line circuit having a plurality of codes applied thereto, a track switch, a signal for clearing traflic over said track switch, a switch control relay momentarily energized by one of said codes for governing said track switch, a signal control relay actuated by another of said codes for energizing said signal, a correspondence relay for registering correspondence between said track switch and said switch control relay, means controlled by said correspondence relay for maintaining energized said actuated switch control relay only until said correspondence relay registers correspondence, and means controlled by said signal control relay for preventing the release of said actuated switch control relay when said signal control relay is energized.

4. In a centralized traffic controlling system for railroads, a control ofiice and a field station connected by a line circuit over which impulses are transmitted to form code combinations, a track switch at said station, signals for governing traflic over said track switch, a switch machine for operating said track switch, a normal control relay for operating said switch machine to its normal position, a reverse control relay for operating said switch machine to its re verse position, means controlled by one-of said code combinations for energizing one of said control relays, means effective only while said switch is not in a position corresponding with the control relay energized for sticking the energized control relay over a circuit including a contact on the other control relay, and additional stick circuit means for sticking either one of said control relays effective only in response to the reception of the proper code combination for clearing one of said signals.

5. In a centralized trafiic controlling system, a track switch operated by a switch machine, a normal code receiving relay and a reverse code receiving relay for governing the operation of track section including a track switch, a switch said track switch to corresponding positions, switch position indicating means, a normal correspondence relay actuated only when said normal code receiving relay and said switch position indicating means are in correspondence, a reverse correspondence relay actuated only when said reverse code receiving relay and said switch position indicating means are in correspondence, a left direction code receiving relay and a right direction code receiving relay, signal control relays, circuits for said signal control relays energized only when one of said direction code receiving relays and one of said correspondence relays are energized, and means for energizing said normal and reverse code receiving relays in response to a code only when said correspondence relays are deenergized.

6.In a centralized traiiic controlling system, a track switch operated by a switch machine, a normal code receiving relay and a reverse code receiving relay for governing the operation of said track switch to corresponding positions, switch position indicating means, a normal correspondence relay actuated only when said normal code receiving relay and said switch position indicating means are in correspondence, a reverse correspondence relay actuated only when said reverse code receiving relay and said switch positionindicating means are in correspondence, a left direction code receiving relay and a right direction code receiving relay, signal control relays, circuits for said signal control relays energized only when one of said direction code receiving relays and one of said correspondence relays are energized, means for energizing said normal and reverse code receiving relays only when said correspondence relays are deenergized, and stick circuits for said normal and reverse code receiving relays energizable only when one of said direction code receiving relays is energized.

7. In a centralized trafiic controlling system, a track switch operated by a switch machine, a normal code receiving relay and a reverse code receiving relay for governing the operation of said track switch to corresponding positions, switch position indicating means, a normal correspondence relay actuated only when said nor mal code receiving relay and said switch position indicating means are in correspondence, a reverse correspondence relay actuated only when said reverse code receiving relay and said switch position indicating means are in correspondence, a left direction code receiving relay and a right direction code receiving relay, signal control relays, circuits for said signal control relays energized only when corresponding direction code receiving relays and correspondence relays are in correspondence, a first stick circuit for said normal and reverse code receiving relays energized only when said correspondence relays are deenergized, and a second stick circuit for said normal and reverse code receiving relays energized only when one of said direction code receiving relays is energized.

8. In a centralized traffic controlling system for railroads, a line circuit having a plurality of difierent code combinations applied thereto, a track switch, a switch machine for controlling said'track switch, switch code receiving relays for controlling said switch machine, correspondence relays energized only when said switch code receiving relays and said track switch are in correspondence, signal circuits for controlling traffic over said track switch, signal code receiving relays forenergizing said signal circuits, en-

ergizing circuits for said code receiving relays controlled bysaid code combinations, stick cir cuits for said code receiving relays, a track relay associated with said track switch, means conence relays energized only when said switch code receiving relays and said track switch are in correspondence, signal'circuits for controlling traffic over said track switch, signal code receiving relays for energizing said signal circuits, energizing circuits for said code receiving relays controlled by said code combinations, stick circuits for said code receiving relays, a track relay and a stop relay associated with said, track switch, means controlled by said correspondence relays for deenergizing the stick circuits of said switch 7 code receiving relays, and means controlled by said track relay and said stop relay for deenergizing the stick circuits of said. signal code receiving relays.

10. In a centralized trafiic controlling system for railroads, a line circuit having a plurality of different code combinations applied thereto, a

track switch, a switch machine for, controlling said track switch, switch code receiving relays for controlling said switch machine, correspondence relays energized only when said switch code .receiving relays and said track switch are in correspondence, signal circuits for controlling traflic over said track switch, signal code'receiving relays for energizing said signal circuits, energiz ing circuits for said code receiving relays controlled by said code combinations, stick circuits for said code receiving relays, a track relay and a stop relay associatedwith said trackswitch, means controlled by said correspondence relays for deenergizing the stick circuits of said switch code receiving relays, means controlled by said track relay for deenergizing the stick circuits of said signal code receiving relays whereby said signal circuits are deenergized, and, additional means controlled by said track relay for dey energizing said signal circuits.

11. In avcentralized trafiic controlling system, a track switch operated by a switch machine, a normal control relay and a reverse control relay for governing the operation of. said track switch, switch position indicating means, a normal correspondence relay and a reverse correspondence relay, means for selectively energizing said control relays, means for stickingthe energized control relay, means controlled by said control relays for selectively energizing said correspond ence relayswhen said indication means and an respondencerelay, means for selectively energizing said control relays from a remote location, means controlled by said control relays for energizing saidcorrespondence relays when said indicating means and an energized control relay are in correspondence, means controlled by said correspondence relays for releasing an energized control relay, means for locally unlocking said switch machine, and means responsive to the unlocking of said switch machine for selectively energizing said control relays.

l3.- In combination, a line circuit having a pinrality of code impulses applied thereto, means for receiving said impulses, a section of track having a track switch associated therewith, a switch machine for controlling said track switch, anormal relay actuated by a first one of said code impulses, areverse relay actuated byasecond one of said code impulses, means controlled by said relays for opcrating said switch machine to corresponding positions, means effective to maintain said relays actuated when once actuated onlyuntil said switch machine is in a corresponding position,

and means responsive to a third one of said code impulses for maintaining said relays actuated when once actuated after said switch machine is in a corresponding position but only until a fourth one of said code impulses is received.

14. In combination, a line circuit having a plurality of code impulses applied thereto, means for receiving said impulses, asection of track having a track switch associated therewith, a switch machine for controlling said track switch, a normal relay actuated by a first one of said code impulses, a reverse relay actuated by a-second one of said code impulses, means controlled by said relays for operating said switch machineto corresponding positions, means effective to maintain said relays actuated when once actuated only until said switch machine is in a' corresponding position, and means responsive, to a third one of said code impulses for maintaining said relays actuated when once actuated after said switch machine is in a corresponding position but only until said track section becomes occupied.

15. In combination, a line circuit having a plurality of code combinations applied thereto, a

tracksection having a track switch associated therewith, a switch machine for controlling said track switch, a plurality of signals for directing traffic over said track switch, a plurality of switch control relays for controlling said switch and a plurality of signal control relays for controlling said signals, means responsive to-a first code combination for actuating one of said switch control relays and means for restoring it to normal after said switch machine attains a position corresponding to said first code combination, means responsive to a second code combination for actuating one of said signal control relays,- means responsive to the occupancy of said'track section for restoring said signal control relay to normal after its response to said second code combination, and means for preventing an actuated switch control relay being restored to normal until said actuated signal control relay is restored to normal.

16. In a centralized traffic controlling systemv for railroads, a track switch, a power operated switch machine for operating said track switch, normally deenergized relay means for controlling the normal and reverse operation of said switch machine when selectively energized, remotely gized only until the selected normal or reverse operation of said switch machine has been completed, and local means for selectively and automatically energizing said relay means when said track switch assumes a position other than the position required by the last selective energization of said relay means by said remotely controlled means.

" 17. In a centralized traffic controlling system for railroads, a track switch, a power operated switch machine for operating said track switch, normally deenergized relay means for controlling the normal and reverse operation of said switch machine when selectively energized, remotely controlled means for at times selectively energizing said relay means, stick circuit means for maintaining said relay means selectively energized only until the selected normal or reverse operation of said switch machine has been completed, local means for selectively and automatically energizing said relay means when said track switch assumes a position other than the position required by the last selective energization of said relay means by said remotely controlled means, and means for preventing local selective energization of said relay means whenever said relay means has been selectively energized by said remotely controlled means to cause the operation of said track switch to a new position.

18. In a centralized traffic controlling system for railroads, a track switch, a switch machine for operating said track switch, normal and reverse switch control relays for when energized respectively'controlling the normal and reverse operation of said switch machine, a normally energized lock relay for preventing the control of said switch machine by said normal and reverse switch control relays when such lock relay is deenergized, and means rendered effective as soon as and whenever said track switch is in correspondence with the particular normal or reverse switch control relay then energized for deenergizing said lock relay and said means remaining effective until said switch control relay is again deenergized.

19. In a centralized traffic controlling system for railroads; a track switch; a switch machine for operating said track switch; switch control relay means for, when selectively energized, controlling the normal and reverse operation of said switch machine; a normally energized lock relay for preventing the control of said switch machine by said switch control relay means when 20. In a centralized traffic controlling system for railroads; a track switch; a switch machine for operating said track switch; a signal for governing traffic over said track switch; normally deenergized switch control relay means for,

when selectively energized, controlling the normal or reverse operation of said switch machine;

a normally energized lock relay for preventing {the control of said switch machine by said switch control relay means when such lock relay is deenergized; means for deenergizing said lock relay whenever and as soon as said track switch is in correspondence with the then energized condition of said switch control relay means; and circuit means for clearing said signal only when said lock relay is deenergized.

21. In a centralized tramc controlling system for railroads; "a track switch; a switch machine for operating said track switch; signals for governing trafiic over said track switch; normally deenergized switch control relay means for, when selectively energized, controlling the normal and reverse operation of said switch machine; a lock relay; signal control relay means; circuit means for normally energizing said lock relay and ineluding contacts open when any one of said signals is cleared and whenever said track switch is in correspondence with the then energized condition of said switch control relay means independently of the condition of said signal control relay means; and circuit means controlled by said signal control relay means for clearing said signals only when said lock relay is deenergized and only when the position of said track switch corresponds to the energized condition of said switch control relay means.

22. In a centralized traflic controlling system; a track switch operated by a'switch machine; switch control relay means for governing the normal and reverse operation of said switch machine; switch pcsition indicating means for indicating a normal, a reverse, or an unlocked condition of said track switch; manually governed means for selectively energizing-said switch control relay means; stick circuit means for maintaining the selectively energized condition of said switch control relay means until said switch position indicating means indicates the correspondence between said track switch and said switch control relay-means; and local means for selectively energizing said switch control relay means in accordance with the last position of said track switch when said switch position indicating means indicates said track switch to be unlocked, said local means acting only provided said switch control relay means is deenergized when said switch is initially unlocked, whereby the accidental or local manual operation of said track switch to a position other than required by said switch control relay means causes the return of said track switch to its'former position.

23. In a centralized trafiic controlling system for railroads; a track switch operated by a switch machine; normally. deenergized switch control relay means for governing the normal'and reverse operation of said switch when selectively energized; switch position indicating means; correspondence relay means energized only when said switch position indicating means indicates said track switch tobe in correspondence with the then energized condition of said switch control relay means; a normally energized lock relay for preventing the control of said switch machine by said switch control relay means when such lock relay is deenergized; manually controlled means for selectively energizing said switch control relay means only when said lock relay is energized; stick circuit means for said switch control relay means for maintaining said switch control relay means selectively energized, said stick circuit means including a front contact of said lock relay; and an energizing circuit for said lock relay including back contacts of said correspondencerelay means; whereby said switch control relay means is maintained selectively energized through'said stick circuit means until said track switch has been operated into correspondence therewith and then restores to a deenergized condition.

24. In a centralized trafiic controlling system for railroads; a track switch operated by a switch machine; normally deenergized-switch control means for governing thenormal and reverse .op-

ence with the then energized condition of said switch control relay means; a normally energized lock relay for preventing the control of said switch machine by said switch control relay means when such lock relay is deenergized; manually controlled means for selectively energizing said switch control relay means only when said lock relay is energized; stick circuit means for maintaining said switch control relay means selectively energized, said stick circuit means including a front contact of said lock relay; an energizing circuit for said lock relay including back contacts of said correspondencerelaymeans,

whereby said switch control relay means is maintained selectively energized by said stick-circuit means only until said track switch has been operated into correspondence with said switch control relay means; signals for governingtrafiic over said track switch; signal control relay means for, when energized, clearing saidsignals; other stick circuit means for maintaining said switch control relay means selectively energized whenever said signal control relay means is energized; and circuit means for clearing said signals'governed by said signal control relaymeans and effective'only when said lock relay is deenergized.

" 25. In combination, a line circuit having a pluralityof code combinations applied thereto, a track section having a track switch associated therewith, a switch machine for controlling said track switch, a plurality of signals for directing traffic over said track switch, a plurality of switch controlrelays for controlling said switch,a

:plurality of signal control relays, means respon- 'ing the restoration of the actuated switch control relay when one of said signal control relays is actuated, means controlled by said signal control relays for clearing said signals, said means'being effective to clear a signal only when one of said switch control rela'ysis actuated and said track switch is in correspondence therewith, and means responsive to the occupancy of said track section or the reception of a third code combination for restoring the actuated signal control relay to normal. 26. In combination, a poweroperated track switch machine for operating a railroad track swltch,. a signal for governing trafiic over said track switch, switch controlrelay means, signal control relay means, switch control circuit means for said switch control relay means, signal control circuit means for said signal control relay means, a stick circuit for said switch control relay means closed only when said signal control relay means is energized, locking means rendered effec tive whenever said switch is in a position corresponding with the then existing energized condition'of' said switch control relay means for preventing operationof said switch to a different position and for rendering energization of said switch control relay means dependent upon its said stick circuit, and means for clearing said signal when said signal control-relay means ,is

energized only when said locking means has rendered the control of said switch control relay means dependent upon its said stick circuit and only when saidswitch control, relay meansis picked up. i

27. In combination; a power operated switch machine for operating a railroad track switch;

signals for governing trafiic over said track switch; switch control relay means; signal control relay means; switch control circuit means for said switch control relay means; signal control circuit means for said signal control relay means; a stick circuit for said switch control relay means closed only when said signal control relay means is energized; a lock relay effective when deenergized to render the energization of said switch control relay means dependent upon its said stick circuit; a circuit for said lock relay including contacts closed only when said switch control relay'means is out of correspondence with said track switch or said track switch is unlocked; circuit means for causing operation of said switch machine in response to the energized condition of said switch control relay means only when said lock relay is picked up; and means for clearing said signalin response to the energized condition of said signalcontrol relay means onlywhen said switch control relay means is picked up, and only switch, manual switch control means for said track switch, manual signal control means for said signal, a lock relay which must be picked up to' close said mo-tor'operating circuit and allow said switch control means to be effective'to govern the operation of said track switch, and which look relay must be dropped away to allow said signal control means to be effective to clear said signal, circuit means for energizing said lock .relay, and means acting only when said track switch has been operated to a position to correspond with the then existing condition of said switch control means to control said circuit means to deenergize said lock relay independently of said signal control means.

29. In an interlocking system; a power operated'track switch; a signal for governing traflic over said track switch; normally deenergized switch and signal control relay means; circuit means controlled by said relay means, when it is energized and rendered effective, for operating said track switch and clearing said signal; a lock relay for rendering-said circuit means effective to operate said track switch when such lock relay is picked up, and for rendering said circuit means effective to clear said signal when such lock relay is dropped away; and control means for said lock relay effective to pick it up only when said switch control relay means is out of correspondence with said track switch or is deenergized and effective to drop it whenever said track switch and said switch control relay means are in correspondence irrespective of the condition of said signal control relay means.

30. In a centralized trafiic controlling system for railroads, a code type communication system connecting a control office with a field station, a power operated track switch at said field station, a signal for governing traffic over said track switch, normal and reverse switch control relays governed over said communication system for respectively closing the normal and reverse operating circuits for said track switch when picked up and rendered. effective, a signal control relay governed, over said communication system for clearing said signal when picked up and rendered effective, a lock relay which must be picked up to render said switch control relays effective and which must be dropped away to render said sig nal control relay efiective, circuit means for en ergizing said lock relay opened to deenergize said lock relay whenever and as soon as said track switch and said control relays are in correspondence and so long as said signal is cleared.

31. In an interlocking system; a power operated track switch; signals for governing trafiic in both directions over said track switch; manual switch control means for said track switch; manual signal control means for said signals; a lock relay, which must be picked up to allow said switch control means to be effective to govern the operation of said track switch, and which must be dropped away to allow said signal control means to be effective to clear said signal; circuit means for energizing said lock relay, and means acting on said circuit means to initially deenergize said lock relay whenever and as soon as said track switch has been operated to a position to correspond with the then existing condition of said switch control means and to maintain said lock relay deenergized when any of said signals are cleared.

32. In an interlocking system, a power operated track switch, signals for governing traific over said track switch in both directions, normally deenergized switch control relay means for governing the power operation of said track switch when selectively energized and rendered effective, a lock relay which must be picked up to render effective said switch control relay means, normal and reverse correspondence relays respectively energized only when said track switch is in normal or reverse position to correspond with the then existing selective energization of said switch control relay means, circuit means for clearing said signals selected through contacts of said normal and reverse correspondence relays and a back contact of said lock relay, and a circuit for energizing said lock relay closed only when both said correspondence relays are deenergized and all said signals are at stop.

33. In a centralized trafiic controlling system for railroads; a track switch; a switch machine for operating said track switch; normal and re verse switch control relays for, when energized, respectively controlling the normal and reverse operation of said switch machine; a normal corswitch control relays and also for preventing a new control of said normal and reverse switch control relays when such lock relay is deenergized; and circuit means for initially energizing said lock relay only when both said normal and reverse correspondence relays are deenergized;v

whereby'said normal and reverse switch control relays must be deenergized prior to each new operation of said track switch.

34. In a centralized traflic controlling system for railroads, a code type communication system connecting a control office with a field station, a power operated track switch at said field station,

signals for governing trafiic over said track switch in both directions for each of its positions, normal and reverse switch control relays governed over said communication system for respectively closing normal and reverse operating circuits for said track switch when picked up and rendered efiective, signal control relays governed over said communication system for selectively controlling said signals when picked up and rendered efiective, a normal correspondence relay energized whenever said track switch is 'in'correspondence with the then picked up normal switch control relay, a reverse correspondence relay energized whenever said track switch is in correspondence with the then picked up reverse switch control relay, a lock relay which must be picked up to render said switch control relays efiective and which must be dropped away to render said sig-, nal control relays effective, circuit means for energizing said lock relay, contacts of said normal and reverse correspondence relays acting on said circuit means to deenergize said lock relay whenever said track switch and said switch control relays are in correspondence, other contacts acting on said circuit means to deenergize said lock relay so long as any one of said signals is cleared,

and circuit means .selectively controlled by saidsignal control relays and including contacts of said lock and said correspondence relays for energizing any particular one of said signals.

THOMAS J. JUDGE. i l 

